A bellwether is any entity in a given arena that serves to create or influence trends or to presage future happenings.

The term is derived from the Middle English bellewether and refers to the practice of placing a bell around the neck of a castrated ram (a wether) leading his flock of sheep. The movements of the flock could be noted by hearing the bell before the flock was in sight.

In politics, the term is more often applied in the passive sense to describe a geographic region where political tendencies match in microcosm those of a wider area, such that the result of an election in the former region might predict the eventual result in the latter. In a Westminster-style election, for example, a constituency, the control of which tends frequently to change, can mirror in its popular vote the result on a national scale.

Professor Yogendra Yadav is an Indian social scientist. He was appointed as a member of the National Advisory Council for the implementation of the Right to Education Act in 2010. He was appointed a Senior Fellow at the Centre for the Study of Developing Societies in 2004.

Yogendra Yadav lists his areas of interest as including "democratic theory, election studies, survey research, political theory, modern Indian political thought and Indian socialism."

In 2009 the International Political Science Association awarded Yadav the first Global South Solidarity Award "in recognition of outstanding work on the politics of the developing world".